Regarding UBI fastmap data CRC failure

[Richard Weinberger]

On Mon, Mar 20, 2017 at 10:47 PM, Ronak Desai
<ronak.desai at rockwellcollins.com> wrote:
> Hi All,
>
> In one of the products with MLC NAND flash, we are using UBI
> filesystem with kernel 3.12.

MLC NAND is currently not supported.

> Fastmap is enabled to reduce the attach time and it works as expected.
> We performed number of powercycles on the unit and never seen a
> continuous failure of attached by fastmap. But, at one occurrence I
> observed that there was a  "fastmap data CRC failure". UBI was
> complaining about not find anchor node error when performing detach
> (that's why was not able to write new fastmap data). It was a
> permanent failure until I reformatted that NAND partition.
>
> I understand that UBI stores fastmap data in initial few KBs of that
> NAND device and it was not able to find spare block in that region to
> store fastmap data. But, I am not able to understand that why UBI end
> up with this situation when it already manages the erasure of the bad
> fastmap blocks?
>
> I would like to know that how I can avoid this situation or get a
> workaround of it. Any advice will be appreciated.

Maybe the error you're facing is due to the lack of MLC support.

Another point is your kernel version, Fastmap saw tons of fixes
and updates in recent kernel. Please make sure that you have
all these fixes. Ideally backport the whole UBI subsystem.

-- 
Thanks,
//richard